This has been fixed in 1.6.3, load your world and the chunks containing the structures you want to preserve, then open the world in snapshots 13w37b and later (not 13w37a!)
Jim Jones
This has been fixed in 1.6.3, load your world and the chunks containing the structures you want to preserve, then open the world in snapshots 13w37b and later (not 13w37a!)